Suction roll silencer



Nov. 3,1959 v E. J. Jus-rus 2,911,042

sucTIoN ROLL SILENCER 5 Sheets-Sheet l `Filed Jan. 24. 1956 Nov. 3, 1959E. J. .n.lsTus 2,911,042

SUCTION ROLL SILENCER Filed Jan. 24. 1956 5 Sheets-Sheet 2 Nov. 3, 1959E. J. JUsTus" 2,911,042

- SUCTION ROLL SILENCER Filed Jan. 24. 1956 5 Sheets-Sheet 5h Nov.3,1959 E. J. Jus-rus SUCTIDN ROLL SILENCER 5 sneetssheet 4 Filed Jan.24. 1956 E. J. JUSTUS SUCTION ROLL SILENCER Nov. 3, 1959 v Filed Jan.24. 195e 5 Sheets-Sheet 5 2,911,042 sUcTIoN RoLL srLENCER Edgar J.Justus, Beloit, Wis., assigner to Beloit Iron Works, Beloit, Wis., acorporation of Wisconsin Application January 24, 1956, Serial No.561,055 8 Claims. (Cl. 162-371) The instant invention relates to papermaking machines, and more particularly, to an improved suction rollequipped with silencing means.

Although the instant invention may have application in other arts, itwill be described primarily in connection with the paper machine art inwhich the instant invention is used to particular advantage. Theconventional suction roll is provided with a perforate rotating cylinderor shell having a stationary suction box operating against the innersurface thereof. The suction box creates a relatively high vacuum whichis transmitted to the sheet of pulp through the perforations in theshell to draw water from the sheet and compact the same. De-

v pending upon the particular location in the paper machine, suctionrolls may vary in diameter from about 16 inches to as muchas about 60inches; and the perforations therein are relatively small in size havingdiameters rangingl from about %2 to about 5%16 of an inch (dependingupon the shell thickness) 'and having a depth (or shell thickness)ranging from about 1 inch to about 4 inches. The suction areas may havevmagnitudes ranging from about 20 to as much as 70 or 80; and suchsuction areas are customarily defined by relatively thin sealing stripsmounted on the suction box and extending axially of the roll.Customarily the sealing strips are about 5X1 inch to 1 inch inperipheral dimension, and this is considered to be the width ,of thestrip required to effect a seal between the rotating shell and thesealing means.

The suction rolls of the prior art, regardless of design 0r manufacture,produce noise when operating at speeds of about 400 ft./ min. or higher;in other words, when the rolls operate at a peripheral speed of about4G() ft./min. or higher, which will also be the speed of the paper and/or felt passing through the machine and over such rolls. Some deviceshave been suggested for reducing this noise, but each of such devicesleaves something to be desired. Suction rolls operating at therelatively high speeds of present-day practice, which are in theneighborhood of 200G-3000 0r more ft./rnin., are ordinarily extremelynoisy, emitting a high pitch sound which is so irritating and wearisometo the operators that most operators have found it necessary to wearearplugs. l

In U. S. Patent No. 2,107,812, issued to Earl E. Berry,

United States Patent O Lloyd Hornbostel and lohn E. Goodwillie, asilencing device in the nature of multiple pressure reducing chambersseparated by sealing strips is suggested, but the greatly increasedoperating speeds lof the present-.day machines tend to make this deviceobsolete.

In U. S. Patent No. 2,274,641, issued to Ernest I. Abbott and .lohn D.Kraus, a silencing device associated with the vacuum sealing strips isalso shown. In this case,

the packing strip is equipped with an extension diverging.,

from the inner periphery of the shell at the offrunning side of thepacking strip so as to provide a slender tapering vent passage ofrelatively great width to control the flow of air entering into theperforations in the roll shell at the offrunning side of the suctionarea. This device is operative for the use shown in the Abbott et al.disclosure,

namely for use with an assembly wherein a felt ycarrying the web istrained over the entire suction area and beyond on the olfrunning sideof the suction area. Recently, however, suction roll arrangements havebeen devised for the purpose of gaining one advantage or another whereineither the felt or the wire with the web thereon is removed from thesurface ofthe suction roll just beyond the oifrunning side of thesuction area. ln such arrangements, it has been found that the Abbott etal. device is much less effective or substantially ineffective. Theinstant invention resides in a discovery of a novel type of sealing:structure for the olfmnning side of the suction area. In particular,the instant sealing structure extends from the olfrunning side of thesuction area Hush against the shell inner periphery for a substantialdistance, substantially greater than the customarily used sealing stripthickness of up to l inch. Instead, such sealing means extends flushagainst (rather than diverging from) the shell inner periphery to beyondthe point at which the web carrying felt or wire is removed from thesuction roll surface. Although it would be expected at first blush thatsuch an enlarged sealing strip would be no more effective `than theregular size sealing strip, it has been found that the instant largesealing strip has unusual silencing powers, particularly at the veryhigh lspeeds 110W used in paper machines. i

It is, therefore, an important object of the instant invention toprovidean improved silencing arrangement for paper machine suction rolls.

It is a further object of the instant invention to provide an improvedpaper machine comprising a rotary perforate suction'roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which reduced pressure is applied to the holes, abelt resistant to air ilow therethrough travelling over the suctionarea-of the shell and away from the shell surface along aline justbeyond the oifrunning side of the suction area, lirst sealing means onthe suction box urged against the shell inner periphery at the oncomingside of said suction area, and second sealing means on the suctionbox'urged against the shell inner'periphery at the ofrunning side ofsaid suction area and extending therefrom flush against the shell innerperiphery to beyond the line at which the belt moves away from theshell.

Other and further objects, features and advantages of 'thepresentinvention will become apparent to those skilled in the art fromthe following detailed disclosure thereof and the drawings attachedhereto and made a part hereof.

On the drawings:

Figure 1 is an essentially diagrammatic view of a paper machinecomprising suction rolls embodying the instant invention;

Figure 2 is an enlarged detail view in sectional elevation ofthe sealingmeans of the instant invention, showing fragmentarilyl associatedstructure;

Figure 3 is a fragmentary elevational view showing the instant sealingmeans in a suction couch roll structure;

Figure 4 is a fragmentary elevational View showing the instant sealingmeans in a suction pickup roll structure;

Figure 5 is a fragmentary elevational view showing the instant sealingmeans in a felt drier press;

Figure 6` is a fragmentary elevational View showing the instant sealingmeans in one type of suction press;

Figure 7 is a fragmentary elevational view showing the instant sealingmeans in another type of suction press;

Figures 8 and 9 are fragmentary elevational views showing differentembodiments; and

Figure l0 is a chart showing the vacuumv loss against i distance inFigures 8 and 9.

erally a paper machine of the instant invention, which is provided witha forming wire F trained over a suction couch roll 11 with suction box12 (which will be described in detail hereinafter) and a turning roll13. 'Ihe forming wire F carries a web W thereon over the suction box 12of the couch roll 11. A suction pickup roll 14 with suction box 15 islapped by a pickup felt 16 and urges the felt 16 against the web W onthe wire F so as to pick the web W from the wire F at the suction box 15and transfer the web W to the suction pickup felt 16. The pickup felt 16is mounted on a plurality of guide rolls 17, 1S, 19, 20, 21 and 22. Thepickup felt 16 passes between a plain press roll 23 and asuction Y pressroll 24 with suction box 25 (which will be described in detailhereinafter) to assist in drying the pickup felt 16 before it passes outaround the suction pickup roll 14. From the pickup roll 14 the pickupfelt 16 carries the Web W to a rst press nip N-1 dened by a press roll26 within the loop of the pickup felt 16 and a suction press roll 27with suction box 28 (which will be described in detail hereinafter)covered by a lower press felt 29. The press felt 29 is mounted on aplurality of guide rolls 30, 31, 32, 33 and 34; and the press felt 29carries the web W to a second press nip N-2 dened by a bare upper roll35 and a lower suction roll 36 with suction box 37 (which will bedescribed in detail hereinafter) covered by the felt 29. As theoifrunning side of the suction area 37 the web W is pulled over a guideroll 3S to separate the web W from the felt temporarily and then returnthe web W to the topside of the felt 29.

A third press nip N-3 is deiined by an upper bare roll 39 and a lowersuction roll 40 with suction area 41 straddling the nip N-3 and coveredby a felt 42 mounted on guide rolls 43, 44, 45 and 46. The web W travelsalong on top of the felt 29 until the end of the felt run 29 whereat thefelt 29 turns about the guide roll 34 and the web tis fed therefrom tothe third press nip N-3 Whereat the web is maintained out of contactwith the felt 42 until the nip N-3 and is then again separated from thefelt 42 by a guide roll 47 at the off running side of the nip N-3.

VThe general character of the structures for the suction boxes 12, 15,25, 28, 37 and 41 of Figure 1 will be discussed separately hereinafter,after a consideration of 'Figure 2 which shows detail features of asealing strip S of essential importance in the instant invention.

Referring to Figure 2, it ywill be seen that a roll shell 50 is shownfragmentarily with holes or perforations 51-60, inclusive, showntherein. A suction area A is shown extending from its oncoming side 61to its offrunning side 62. At the oncoming side 61v a normal sealingstrip 63 mounted for slight radial movement in a packing gland 64 isresiliently urged against the inner periphery of the shell 50 by aspring 65 or other suitable means. The packing gland 64 is, of course,mounted on the suction box 66 indicated only fragmentarily. As is wellknown, the suction box or gland is permanently mounted within the rollshell 50 and connected through axially aligned conduits to a vacuum pumpor similar device for creating a vacuum in the suction area. A andreducing the pressure in the holes 51a and 51 exposed to the suctionarea A.

As` will be appreciated, the normal sealing strip 63 has a relativelyshort peripheral dimension d (or width) in the nature of from about 2%,to about l inch and this is a sucient width to eifect a seal between theinner periphery of the shell 50 and the strip 63 per se.

In contrast, a sealing strip 67 of the sealing strip assembly Sembodying the instant invention has a peripheral dimension D'of fromabout 2 to about 5 times the width d that is required to form a seal. Ashere shown, the width a' is 3XL inch, whereas the width D is 3% inches,for a typical embodiment of the instant invention. Although it would beexpected that the use of the much wider sealing strip 67 would result innothing Vmore than a more perfect seal between the strip 67 and theinner periphery of the roll shell 50 and also result in a greater amountof wear on both members, the actual result is a very substantial andunique silencing elect. The sealing strip 67 has its `top surface 67amaintained flush against the inner periphery of the roll shell 50throughout the entire width D of the sealing strip 67. As will beappreciated, Abbott (Patent No. 2,274,641) has suggested spacing theoffrunning surface of a sealing strip away from the shell periphery soas to form a divergent path which permits air to enter between thesealing strip and the roll shell through a restricted path along theofrunning side of the packing. It has been found that the Abbottstructure may be used with effect in a suction box such as the suctionbox 28 shown at the first press nip N-1g but the Abbott structure is noteffective in any of the other suction boxes shown in Figure 1. Thereason for this is now believed to be that in the suction box 23 thefelt 29 with the web W thereon is urged against the outer periphery ofthe roll 27 until substantially beyond the suction box 28.

In contrast, in the arrangement shown in Figure 2, it will be noted thatthe web W carried on a felt F is trained over the suction area A of theshell 50 and then away from the shell surface along a line LL justbeyond the oifrunning side 62 of the suction area A. Also, it will benoted that the sealing strip 67 is urged against the shell innerperiphery at the off-running side 62 of the suction area A and extendstherefrom flush against the shell inner periphery to beyond the line Lat which the felt F moves away from the shell 50. This results in aunique silencing eifect.

Although it is not desired to limit the invention to any particulartheory, it is believed that the reduced pressure created in the suctionarea A is retained in the holes 52, 53 and perhaps 54 and `55, so thatthe forward portion 67b of the sealing strip 67 functions substantiallyas the sealing strip 63, merely to eifect the desired seal. However, thefelt F is then directed away from the surface of the shell 50 atapproximately along the line L (which extends axially of the roll). Asthe felt F breaks away from the surface of the shell 50, it will beappreciated that air will start to enter through the tops of the holes,such Vas at 58. Mere regulation of the rate at which the felt separatesfrom the shell 50 in order to control the flow of air into holes such asthe holes 56 and 57 would probably be effective, if such were possibleas a practical matter. However, the resiliency of the felt (or of a wirecarrying the Wet web) makes precise control here a practicalimpossibility. Instead, extremely high vacuums in, for example, the hole56 will tend to hold the felt F thereagainst or perhaps to distort thefelt F as indicated in the drawing to a limited extent. In this Waysubstantial volumes of air cannot flow rapidly into a hole such as thehole 56 Which has a very high vacuum; whereas after some initial leakageof air into a hole such as the hole 57 the vacuum may have been reducedand the entrance of the remaining air into the hole 57 will not causeany appreciable noise. In this way it will be seen that the travelingfelt F (or wire W) may coact with the shell 50 because of the resilientcharacter of the felt F So as to function as its own check valve inpreventing substantial quantities of air vfrom entering holes having ahigh vacuum. As has been mentioned, it is not desired to limit theinvention to any particular theory, but it is believed that theforegoing explanation which has been developed primarily by hindsightdescribes generally the phenomena here involved which will account forthe superior performance ing of the diverging portion of his packinggland. Wearing of the Abbott packing gland will, of course, create aneed for constant adjustment 4and Abbott provides for such adjustment.

usual sealing strip materials which include-hard resins,-

wood, layers of packing, or the like is provided with an oncoming 67Cand an olrunning 67d leg or ridge. The legs 67e and k67d extend radiallyinwardly from the main body of the sealing strip 67. Guide walls 68a and68b are provided in the packing gland 68 for receiving the oncoming leg67C and permitting limited axial movement therebetween. In similarmanner, walls 68e and 68d slidingly receive the oflrunning leg 67d ofthe packing strip 67. (For convenience, arrows are shown in the instantFigure 2 and each of the remaining igures to show the direction in whichthe shell 50rotates.)

Resilient means in the form of a resilient pneumatic tube 69 made ofrubber or suitable flexible material and connected to a source of air(not shown) under pressure is seated between the guide walls 68a and 68hfor resiliently urging the oncoming packing leg 67C toward the innerperiphery of the shell 50. In like manner, similar pneumatic means 70are provided between the walls 68C and 68d for resiliently urging theotrunning sealing strip leg '67d against the inner periphery of the roll50. In this way, any wear at either-the forward or the rear end of theworking surface67a of the sealing strip 67 will not cause separationbetween the sealing strip surface 67 and the shell 50. Instead, thespaced resilient means 69 and 70 functioning to urge opposite ends ofthe sealing strip `67 against the roll shell 50 will compensate for anywear on the sealing strip surf-ace 67a and continuously maintain thesealing strip surface 67a against the inner periphery of the shell 50.It will be appreciated that the resilient means 69 and -70 positioned inspaced relation from each other and coacting Y with the oncoming andoffrunning sides, respectively,.of

the sealing strip 67 serve to maintain constant accurate adjustmentautomatically.

The sealing strip legs 67c and 67d are slightly smaller than the spacebetween the walls 68a and 68b, and the walls 68e and 68d, so as topermit sliding'movement therebetween and also slight tilting movement inthe event that either the oncoming or oirunning portion of the topsurface 67a should wear faster than the other. In order to preventexcessive leakage of air between the sealing strip 67 and the forwardgland wall 68, a small pneumatic sealing device 71 is provided inthewall 68a in the form of a rubber tube `which connects to a source of airand is urged against the sealing strip 67 to form a seal. A similarpneumaticmember 72 is mounted in the rear wall 63d for cooperation withthe offrunning packing strip leg 67d. A u

As shown in Figure 2, the suction area A is covered is shown in the formof the felt F with the web W carried thereon. it will also beappreciated that a forming wire with the web thereon willV `function ina similar ymanner; but the forming wire and the usual lightweightfeltswill function in a different manner if the paper web is removedtherefrom before or during travel over the sealing strip assembly S.These distinctions will be explained hereinafter. In general, however,the instant invention may be used to the greatest advantage if the belt(in the form of a web or a wire with the paper web thereon) is removedfrom thekshell surface along a line L which is within the middleone-half of the sealing strip 67 Referring now to specific embodimentsof the instant invention, in Figure 3, it will be seen that the suctioncouch roll 111 is shown (fragmentarily) with the suction box 112 shownpartially therein. The suction box 1i rmounts a first sealing strip 12aurged against the inner periphery of the shell 11a at the oncoming sideof the suction area A--11. The'traveling `forming wire F carrying thewet web W is trained over the suction area A-11 and away from thesurface of the Ashell 11a along a line L-11 just beyond the oiirunningside of the suction area A-111 (which is defined by the oncoming edge ofthe sealing assembly `S-1-1). As will be noted, the sealing assembly`S`11 has the same structure as the sealing assembly `S`of Figure 2 andthe sealing assembly S-11 extends from the olfrunning side of thesuction area A-1-1 ush yagainst the inner periphery of the shell 11a tobeyond the line L-'11 at which `the Wire F and the web W move away fromthe shell 11a. The line L-11 is aligned approximately with the middle ofthe sealing strip assembly S-1=1. The use of the sealing strip as-'sembly S-11 in the suction couch lroll'll has been found to result invery superior silencing of the noise ordinarily created by the suctionroll 1,1. As will be appreciated, there is a distinct advantage in beingable to remove the wire F from the surface of the shell 11a along a lineL-11 just beyond the oifrunning side of the suction area A-11, andbefore exposure to atmospheric pressure beyond a sealing strip (notshown) at theoifrunning side of the suction area A-ll. This is becausethe suction couch roll 1'1 tends to retain droplets of water in theperforations 11b therein and once the full atmospheric pressure isavailable in the inside of the suction roll 11 centrifugal force willtend to throw the droplets of water back ou-t onto the forming wire F.The instant invention permits the removal of the forming wire attheYdesired location without causing excessive noise.

Referring now to Figure 4, it will be seen that Figure 4 showsfragmentarily a shell 14a of the suction pickup roll 14, as shown inFigure l, having a suction box 15 shown fragmentan'ly therein for thepurpose of defining a suction area A-14. Actually, the suction areaAv-14 is divided into a high vacuum area H dened by a peripherallyspaced pair of sealing strips 15a and 15b .whereat maximum vacuum isapplied for the purpose of picking up the web W from the forming wire F.The web W is picked up on the pickup felt ,16 which is As mentioned, thesuction area A-14 includes a rst oncoming high vacuum suction area H andthen a second low vacuum suction larea L which employs only enoughvacuum to retain the felt 16 andthe web W on the surface of the i shell14a. The traveling pickup felt `16 is thus trained lwith `a belt that isresistant to air flow therethrough which over the suction area A-1'4 ofthe shell 14a and away from the surface of the shell l14a along a lineL-14 just beyond the otfrunning side fof the suction area A414 which isdefined by the oncoming edge of a sealing strip assembly S-14. Thesealing strip assembly S-14 has the same structure as the sealing stripassembly S of Figure 2 and S-11 of Figure 3 and functions in the samemanner. The felt 16 with the web W retained thereagainst (on the bottomside) is trained away from the shell surface along the line L-1f4 whichis aligned approximately with the middle of the sealing strip assemblyS-14. Again, a superior silencing effect is obtained by the use of thesealing strip assembly S-14 and the additional operating advantage ofseparating the felt 16 and the web W from the shell 14a just beyond thesuction area A-14 is obtained. As here shown fragmentarily, a saveallpan 73 is conveniently interposed between the shell 14a and the felt 16at the offrunning side so as to prevent droplets of water from beingshown off the shell 14 that a suction area A24 is defined by a lirstsealing means 25a on the suction box 25 (shown fragmentarily) at theoncoming side of the suction area A-24 and a sealing strip assembly S-24also mounted on the suction box 25 at the olfrunning side of the suctionarea A-24. In

Vthis particular assembly, the suction area A-24 is mounted above thepress nip N-4 which has its maximum point of pressure substantiallyalong the line L-24 at which the felt 16 is carried from the surface ofthe suction roll 24 and transferred onto the surface of the plain pressroll 23. The line L-24 is aligned approximately with the middle of thesealing strip assembly S-24, which has the same structure as that shownby S in Figure 2. The general principles here are the same as thosehereinbefore set forth, with the exception that the felt 16 is backed bythe roll 23 rather than carrying a web W thereon. Superior silencing isobtained using this structure. v

Referring now to Figure 6, which shows the coopera- I tion between thepress rolls 35 and 36 at the press nip N-2, it will be seen that thepress felt 29 with the web W thereon is passed through the nip N-2. Atthe nip N-2 it is desired to retain the web W plus the felt 29 against-the surface of the upper bare roll 35, so the web W and the felt 29 areseparated from the surface of the suction roll 36 along a line L-36 atapproximately the line of maximum nip pressure. In the suction roll 36there is provided a suction area A-36 defined by a first sealing strip37a carried by the suction box 37 at the oncoming side of the suctionarea A-36 and a sealing strip assembly S36 at the olrunning side of thesuction area A-36, also mounted on the suction box 37 which is shownfragmentarily. Again, the sealing strip assembly S-36 has the samestructure as that shown in Figure 2 and the sealing strip assembly S-36extends substantially an equal distance on either side of the line1.-36. Here again, a superior silencing effect is obtained.

Referring now to Figure 7, which shows the cooperation between the upperbare roll 39 and lower suction roll 40 to define the press nip N-3 asshown in Figure l, it will be seen that the web W is placed on thesurface of the bare roll 39 before it reaches the line of maximumpressure at the nip N-3 and is retained on the bare roll surface 39 atthe oifrunning side of the nip N-3, so that the web contacts the feltonly along the line of maximum pressure L-39. In the suction roil 40 thesuction box 41 mounts the first sealing means 41a and the sealingassembly S41 to define therebetween a suction area A-41. The suctionarea A-41 straddles the nip N-3 or the line of maximum pressure L-39, sothat the felt 42 which is trained over the entire suction area A-41 maybe dewatered on opposite sides of the line of pressure L-39. The felt42, as here shown, is separated from the suction roll 40 along the lineL-40 which is intermediate the oncoming and offrunning edges of thesealing assembly `S-41. As here shown, the line L-40 is near theoffrunning edge 74 of the sealing assembly S-41, and this isadvantageous because the felt 42 without the web W thereon is much morepermeable to air and permits a slight amount of air to pass through thefelt 42 andinto the holes at 4Gb passing over the sealing assembly S-41before separation between the felt 42 and the roll 40 takes place alongthe line L-40. In fact, using the presently employed felts havingreasonably high permeability, it has been found that actual separationbetween the felt and the roll need not take place until after thesealing assembly S-41 has been passed (as long as the sealing assemblyS-41 is of suiicient peripheral width) and the paper web W has beenseparated from the felt during substantially all of its travel acrossthe sealing assembly S-41. The sealing assembly S-41 should be fromabout 2 to about 5 times the peripheral width that is required to make aseal and in the special instance just mentioned it is preferably 3 to 5times this width. rIhe essence of the instant invention being thesubstantial sealing of the bottoms of the holes in the 8 shell for anappreciable amount of travel so that an initial amount of air can beslowly forced into these holes through the top, preferably through theautomatic check valve which a resilient wire or web tends to form withthe outer surface of the roll, but also through a generally permeablefelt which has no paper web on the outer surface thereof.

Referring nowto Figures 9 and l0, it will be seen that a suction rollshell 50 is indicated in cooperation with a sealing strip assembly S-Stlof the same type as that hereinbefore described, for example, in Figure2, which separates a high vacuum area A-Stl from an atmospheric pressurearea B-50 by a width D-50 that is comparable to the distance D ofFigure2. It will also be seen that both the web W-St) and the felt F-50 areseparated from the surface of the shell 50 before the perforation 50a inthe shell 50 which is closed at the bottom by the sealing assembly S-50can pass over the sealing assembly S-Stl. Actual-ly a vacuum loss occurscontinuously in each of the perforations or holes 50a, 50]), up to 50e;and Figure l0 shows generally the rate at which the vacuum loss occursby the line 51. The line 51 plots the vacuum V against the distance Dwhich the shell Si) has traveled over the sealing assembly S-Si). Asshown in Figure 10 an initial relatively high vacuum V1 is maintained inthe hole 50e just as it crosses on to the sealing assembly S-50 and thevacuum in each hole decreases to substantially atmospheric pressure V0by the time the hole reaches the position of the hole 50a at theoifrunning side of the sealing assembly S-Sl).

It will be appreciated that the curve 51 shows an ideal rate of vacuumloss which is sufficiently slow to prevent the creation of noise. Thisalso involves starting with an initial vacuum V1 in the suction areaA-'tl which is a sufficiently low vacuum to be eifectively lost in thedistance D50.

In contrast, Figure 8 shows different operating conditions. In Figure 8,a roll shell 60 is shown fragmentarily Wrapped by a felt F-60 carrying aweb 9V-60; and the felt F-60 and the web W-60 are retained on thesurface of the shell 60 for the entire distance D-e@ of the sealingassembly S-60. The sealing assembly S-t), of course, separates a highvacuum area A-il from an atmospheric pressure area B-l) in the mannerliereinbefore described. The vacuum area A-ii imparts an initial vacuumV2 (Figure l0) in a hole 60d exposed thereto that is a greater vacuumthan the vacuum V1 of the suction area A-Sl. If the relatively shortersealing assembly S-Sl) were employed with the shell 60 under theconditions indicated in Figure 8, the vacuum rate of drop would beindicated by the curve 61 down to the point V3, at which point the hole60a would break over the end of the sealing assembly S-50 and the vacuumloss would take place abruptly along the dotted line 61a, with theresult that noise would be created. Such noise would, of course, be muchless noise than that ordinarily created, because the vacuum V3 has beenreduced to at least about 30% of the initial vacuum V2. For this reason,a definite silencing effect is obtained by the -use of a sealingassembly S-50 which has a length or dimension D-50 within the rangespecified for D of Figure 2. On the other hand, the sealing assembliescannot have excessive distances and it has been found that a slightlyincreased distance D- can be added to the offrunning side of the sealingassembly S-S so as to obtain a sealing assembly S-60 which will functionto serve the purpose. This additional dimension D-70` permits a morerapid rate of vacuum loss than a sealing assembly wherein the sealingstrip is flush against the inner periphery of the shell 60 for itsentire dimension, because the portion D-70 of the sealing assembly S-@provides an extension diverging from the inner periphery of the shell 60at the orunning side of the sealing strip assembly S`60 so as to providea slender tapering vent passage to control the flow of air entering intoperforations in the roll shell 60. In this way the vacuum drop followsthe f Ycurve 6112. The curve 61ib drops relatively4v abruptly toatmosphericA pressure V0, but only for approximately the `last 30% ofthe vacuum drop. VThe tapering vent' 62 shown in Figure 8 is, of course,exaggerated; but its function is clear. Essentially, the main body ofthe'sealing assembly S-60 which is ush against the inner periphery ofthe shell 60 is maintained thereagainst for a sufficient distance tocontroll the vacuum' loss through about 70% thereof. After the vacuumloss-hasreached the point V3, more abrupt vacuum loss may bepermittedwithout the creation of noise; Thisis -done using a taperingvent 62. Althouglrthe vent is formedstructurally along the linesindicated in said U.S. Patent No. 2,274,641, the vent 62 used in thepresent invention differs substantially from the vent of said U.S.Patent No. 2,274,641 in that the sealing assembly S60 is providedinitially with a sealing portion D-80 of substantial length flushagainst the inner periphery of the shell 60 to control the loss of atleast about 70% of the vacuum V2.

It will be understood that modifications and variations may be effectedWithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

l. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which reduced pressure is applied to the holes, atraveling felt trained over the entire suction area of the shell andaway from the shell surface along a line just beyond the offrunning sideof the suction area, first sealing means on the suction box urgedagainst the shell inner periphery at the oncoming side of said suctionarea, and second sealing means on the suction box urged against theshell inner periphery at the ofirunning side of said suction area andextending therefrom flush against the shell inner periphery to beyondthe line at which the felt moves away from the shell, and for such adistance as to effect a substantial reduction in noise caused byrotation of the shell.

2. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which reduced pressure is applied to the holes, abelt resistant to air ow therethrough traveling over the entire suctionarea of the shell and away from the shell surface along a line justbeyond the offrunning side of the suction area, first sealing means onthe suction box urged against the shell inner periphery at the oncomingside of said suction area, and second sealing means on the suction boxurged against the shell inner periphery at the offrunning side of saidsuction area and extending therefrom flush against the shell innerperiphery to beyond the line at which the belt moves away from theshell, and for such a distance -ingfelt carrying a web through saidpress nip and trained overthe entire suction area of the shell and away:from .theshell surface along a line just beyond the oirunning side ofthe suction area, first sealing means on the suction box urged againstthe shell inner periphery at the oncoming side of said suction area, andsecond sealing means on the suction box urged against the shell innerperiphery at the offrunning side of said suction area and extendingtherefrom flush against the shell inner periphery to beyond the line atwhich the felty moves away from the shell, and for such as distance asto effect a substantial reduc# tion in noise caused b'y' rotation of theshell.

5. In a paper machine,- a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which lreduced pressure is applied to the holes, atraveling felt trained over the suction area of the shell, a web carriedon said felt over the entire suction area, means guiding the web awayfrom the shell along a line just beyond the offrunning side of thesuction area, first sealing means on the suction box urged against theshell inner periphery yat the oncoming side of said suction area, andsecond sealing means on the suction box urged against the shell innerperiphery at the offrunning side of said suction area and extendingtherefrom flush against the shell inner periphery to beyond the line atwhich the web moves away from the shell, and for such a distance as toeffect a substantial reduction in noise caused by rotation of the shell.

6. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which reduced as to etect a substantial reductionin noise caused by rotation of the shell.

3. In a paper machine, a rotary perforate suction couch roll shellhaving a plurality of holes, a suction box within the shell deiining asuction area on the shell at which reduced pressure is applied to theholes, a forming wire carrying a wet web trained over the entire suctionarea of the shell and away from the shell surface along a line justbeyond the offrunning side of the suction area, first sealing means onthe suction box urged against the shell inner periphery at the oncomingside of said suction area, and second sealing means on the suction boxurged against the `shell inner periphery at the offrunning side of saidsuction area and extending therefrom liush against the shell innerperiphery to beyond the line at which the wire moves away from `theshell, and for such a distance as to effect a substantial reduction innoise caused by rotation of the shell.

4. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a press roll defining a press nip with said shell, asuction box Within the shell defining a suction area on the shell at thepress nip at which reduced pressure is applied to the holes, atravelpressure is applied to the holes, a traveling felt trained overthe suction area of the shell, a web carried on said felt over theentire suction area, means guiding the web and felt away from the shellalong a line just beyond the offrunning side of the suction area, firstsealing means on the suction box urged against the shell inner peripheryat the oncoming side of said suction area, and second sealing means onthe suction box urged against the shell inner periphery at theoffrunning side of said suction area and extending therefrom ush againstthe shellinner periphery to beyond the line at which the web and feltmoves away from the shell, and for such a distance as to effect asubstantial reduction in noise caused by rotation of the shell;

7. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suctionarea on the shell at which reduced pressure is applied to the holes, atraveling felt trained over the entire suctionarea of the shell, a webcarried by said felt, means defining a press nip at the suction area topress the web thereat and remove the web from the felt before theoffrunning side of the suction area, first sealing means on the suctionbox urged against the shell inner periphery at the oncoming side of saidsuction area, and second sealing means on the suction box urged againstthe'shell inner periphery at the offrunning side of said suction areaand extending therefrom ush against the shell inner periphery two tofive times the peripheral disstance of 3A to l inch required to effectthe seal between Vthe shell and the sealing means, and for such adistance as to effect a substantial reduction in noise caused byrotation of the shell.

8. In a paper machine, a rotary perforate suction roll shell having aplurality of holes, a suction box within the shell defining a suction-area on the shell at which reduced pressure is applied to the holes, abelt resistant to air ow therethrough traveling over the entire suctionarea of the shell and away from the shell surface along a line justbeyond the ofrunning side of the suction area, first sealing means onthe suction box urged against the shell inner periphery at the oncomingside of said suction area, second sealing means on the suction box urgedagainst the shell inner periphery at the otfrunning side of said suctionarea and extending therefrom flush against the shell inner periphery tobeyond the line at which the belt moves away from the shell, and forsuch a dstauce'as to effect a substantial reduction in noise caused byrotation of the shell, and spaced resilient means urging the oncomingand oirunning sides of said second sealing means against the shell innerperiphery.

' References Cited in the le of this patent UNITED STATES PATENTS1,718,574 Millspaugh June 25,` 1929 12 Berry et al Feb. 8, 19,38 Abbottet al. Mar. 3, 19.42 Goodwillie et al May 9, 1944 Hornbostel Feb. 20,1945 Goodwillie et al Feb. 23, 1954 Hornbostel Jan. 31, 1956 Kelly Dec.4, 1956 FOREIGN PATENTS Germany v June 30, 1909 Germany June 27, 1939

